Podcast
Questions and Answers
What is the characteristic of garnet and spinel that eliminates the need for cutters to consider pleochroism?
What is the characteristic of garnet and spinel that eliminates the need for cutters to consider pleochroism?
- They are doubly refractive
- They have a distinct pleochroic effect
- They are singly refractive (correct)
- They display a strong fluorescence
Which of the following is a mixture of pyrope and almandine?
Which of the following is a mixture of pyrope and almandine?
- Hessonite
- Tsavorite
- Demantoid
- Rhodolite (correct)
What is the primary source of rhodolite since the 1960s?
What is the primary source of rhodolite since the 1960s?
- South America
- East Africa (correct)
- Asia
- South Africa
What is the coloring agent in tsavorite?
What is the coloring agent in tsavorite?
What is the type of garnet that is often used in inexpensive, mass-market jewelry?
What is the type of garnet that is often used in inexpensive, mass-market jewelry?
What is the chemical composition of demantoid?
What is the chemical composition of demantoid?
What is the characteristic of color-change garnets?
What is the characteristic of color-change garnets?
What was previously identified as ruby but later recognized as spinel?
What was previously identified as ruby but later recognized as spinel?
What is the primary characteristic that distinguishes rhodolite from other red garnets?
What is the primary characteristic that distinguishes rhodolite from other red garnets?
Which type of garnet is typically classified by its physical and optical properties?
Which type of garnet is typically classified by its physical and optical properties?
What is the primary reason for the high value of large tsavorite stones?
What is the primary reason for the high value of large tsavorite stones?
What is the primary use of pyrope-almandine garnets?
What is the primary use of pyrope-almandine garnets?
What is the characteristic of demantoid that distinguishes it from other types of garnet?
What is the characteristic of demantoid that distinguishes it from other types of garnet?
Which type of garnet is often used as a substitute for ruby?
Which type of garnet is often used as a substitute for ruby?
What is the primary characteristic of color-change garnets?
What is the primary characteristic of color-change garnets?
What is the primary difference between hessonite and other types of garnet?
What is the primary difference between hessonite and other types of garnet?
Which type of garnet is typically mined in East Africa?
Which type of garnet is typically mined in East Africa?
What is the primary characteristic of garnets that distinguishes them from other minerals?
What is the primary characteristic of garnets that distinguishes them from other minerals?
A cabochon that has a curved, undercut bottom, designed to lighten the tone of the gem is referred to as ?
A cabochon that has a curved, undercut bottom, designed to lighten the tone of the gem is referred to as ?
When a chemical is substituted for another in the crystal structure of a mineral , what has happened?
When a chemical is substituted for another in the crystal structure of a mineral , what has happened?
What is the most valuable orange garnet?
What is the most valuable orange garnet?
In Spinel, the higher the chromium content, the stronger what?
In Spinel, the higher the chromium content, the stronger what?
Study Notes
Garnet and Spinel
- Garnet and spinel are singly refractive, eliminating the need for cutters to consider pleochroism.
- Most red garnets, including the popular rhodolite, are mixtures of pyrope and almandine.
- Garnets belong to a group of minerals with the same crystal structure but slightly different chemical composition.
- Rhodolite, the most valuable red garnet, has a dark purplish red to light reddish purple hue.
- Many garnets are mixtures of two or more garnet species.
- Gemologists classify garnets by their physical and optical properties, but many dealers sell garnets on the basis of color or origin.
Garnet Species
- Hessonite is the transparent orange to cinnamon-colored variety of the grossular species.
Tsavorite
- Tsavorite is colored by vanadium, and the best is pure green or green with a slight amount of blue.
- Tsavorite is mined mostly in East Africa.
- Large tsavorite rough is extremely rare, so there’s a huge increase in value between small and large fashioned stones.
Spinel
- Many historically important red gems, long identified as ruby, were recognized as spinel in the 1800s.
- Demantoid, the transparent green variety of andradite, is colored by a mixture of chromium and iron.
Garnet Sources and Uses
- East Africa has been the most important source of rhodolite since the 1960s.
- Huge numbers of dark-toned, reddish brown, calibrated pyrope-almandine garnets are used in inexpensive, mass-market jewelry.
Garnet and Spinel
- Garnet and spinel are singly refractive, eliminating the need for cutters to consider pleochroism.
- Most red garnets, including the popular rhodolite, are mixtures of pyrope and almandine.
- Garnets belong to a group of minerals with the same crystal structure but slightly different chemical composition.
- Rhodolite, the most valuable red garnet, has a dark purplish red to light reddish purple hue.
- Many garnets are mixtures of two or more garnet species.
- Gemologists classify garnets by their physical and optical properties, but many dealers sell garnets on the basis of color or origin.
Garnet Species
- Hessonite is the transparent orange to cinnamon-colored variety of the grossular species.
Tsavorite
- Tsavorite is colored by vanadium, and the best is pure green or green with a slight amount of blue.
- Tsavorite is mined mostly in East Africa.
- Large tsavorite rough is extremely rare, so there’s a huge increase in value between small and large fashioned stones.
Spinel
- Many historically important red gems, long identified as ruby, were recognized as spinel in the 1800s.
- Demantoid, the transparent green variety of andradite, is colored by a mixture of chromium and iron.
Garnet Sources and Uses
- East Africa has been the most important source of rhodolite since the 1960s.
- Huge numbers of dark-toned, reddish brown, calibrated pyrope-almandine garnets are used in inexpensive, mass-market jewelry.
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Description
This quiz covers the characteristics and types of garnet and spinel, including their optical properties and species.
